It's no surprise that Disney animated films are a popular playground for fan theories in various places across the web. This includes one of Disney's newest films, Moana. Moana fan theories run the gamut from explaining why she has a mystical connection to the ocean to how Maui managed to relieve her of her boat. Some of the following Reddit theories seem more plausible than others, but any of them may be exactly on point.
Redditor u/SketchesFromMidgard speculates that since the Heart of Te Feti is able to grant life to vegetation, humans, and animals, it also protects Moana from danger while in her possession. Previously, Maui took the Heart from its rightful place and faced the wrath of lava monster Te Ka. Since Maui had the Heart, a strike from Te Ka did not burn or end him but only knocked the stone into the ocean depths.
Gramma Tala gives the stone to Moana and almost immediately afterward becomes sick and passes away. The stone kept Gramma Tala from harm all of those years, so it does the same for Moana on her journey to return it. That is why Moana survives the storm that washes her up onto Maui's island, the fall into the Realm of Monsters, and the confrontation with the coconut assailants.
Moana sets sail to find Maui so he can lead her to the rightful location of the Heart of Te Fiti. Following a terrible storm, the princess wakes up on an island whose only inhabitant is Maui. Redditor u/87StickUpKid theorizes that the ocean took the life of Moana in the storm so that she could be reborn as a demigod.
Later in the film, Moana is able to push a stone statue over, fight hundreds of coconut people assailing her boat, and even free dive to the bottom of the ocean to retrieve the Heart. These do not seem to be things a mortal human can do, u/87StickUpKid claims, but a demigod like Maui can. The Redditor further notes that Moana enters and leaves the Realm of Monsters, a place where Maui says no mortals can go.
During the course of the movie, Maui asks why the ocean would choose a young girl with no sailing experience to return the Heart of Te Fiti to its rightful location. Why not have Maui return what he took? Or why couldn't the ocean, which is shown to have anthropomorphic traits, replace the stone itself? Redditor u/graaah speculates that the ocean knows Maui is afraid of Te Ka and will not willingly take on the task. Maui is required for the mission, but another person is needed to push the demigod into action.
The ocean doesn't know where to return the Heart, but Maui does. Moana is chosen for her ability to persevere and drive Maui into action to complete his part of the ocean's plan.
Moana finds a cavern filled with the boats of her ancestors, but the boat she takes on the voyage - according to Redditor u/Underwateraven - is a special vessel given to her by the ocean. When Moana sees a vision of her ancestors exploring the seas, there is no trace of the boat she eventually sails beyond the reef. That boat also happens to be just the right size to hold Maui, Hei Hei, and Moana, while also being swift enough to maneuver through awkward passages. Furthermore, Moana's boat has a unique symbol that is also seen in the sand on both occasions when the ocean gifts Moana a shell. The Heart has similar markings on its surface.